Thermographic reproduction composite wherein a calcium carbonate layer is effected by a transferred heat-sensitive material



THERMOGRA OMPOSI WHEREIN A CALCIUM CARB TE LAYER IS E -CTED BY A TRANSFERRED HEAT-SENSITIVE MATERIAL Y Filed April 28, 1960 No v. 5, 1963 D. A. NEWMA 3,109,748

c REPRODUCTIO [III/Willi- Z! INVENTOR Douglas J4. JVW/fld/Z 21 BY United States Patent THERMOGRAPHIC REPRODUCTION CGMPOSITE WHEREIN A CALCIUM CARBONATE LAYER IS EFFECTED BY A TRANSFERRED HEAT-SENSI- TIVE MATERIAL Douglas A. Newman, Glen Cove, N.Y., assignor to Columbia Ribbon and Carbon Manufacturing Co., 1126-, Glen Cove, N.Y., a corporation of New York Filed Apr. 28, 1960, Ser. No. 25,450 6 Claims. (Cl. 117-365) This invention relates to novel heat-sensitive duplicating elements for producing exact copies directly from an imaged original sheet under the effects of infrared radiation.

The necessity and advantage of producing duplicate copies of an original sheet is well-known. To satisfy this need, many diverse methods have been developed and are in wide use today.

The most common duplicating medium is the carbon paper transfer sheet. Although these sheets are universally employed, they are recognized to have certain important disadvantages. For instance, since they are heavily pigmented with carbon black, they cause staining of the typists hands and clothing. Likewise, the duplicate carbon copies which are produced are dirty to the touch causing staining of the hands and smudging of the formed images. Another disadvantage of the socalled carbon paper transfer sheets is that they can only be used in the manual production of duplicate copies through the use of imaging pressure and have no utility in the automatic, so-called thermographio processes of producing duplicate copies.

Recognizing these many disadvantages, the art has developed a variety of duplicating systems which require no carbon paper and which produce duplicate copies directly from an original sheet through the use of infrared radiation. Some of these systems depend upon the reaction of dye components or chemical salts to form the color in the heated areas. For instance, a copy sheet carrying colorless unreacted dye components is placed together with an original sheet and passed through a Thermo-Fax machine. Under the elfects of heat generated by the imaged areas of the original sheet, the dye components react and form colored dye images on the copy sheet in areas cor-responding to the imaged areas of the original sheet. Although such systems are suited for some needs, they also have their disadvantages. Since color formation depends upon the concentration of the chemicals and the use of a certain amount of heat as a catalyst, these sheets must be carefully prepared and stored under controlled condtions of heat. !The sheets have the tendency to lose their effectiveness with age as the chemicals contained therein become reduced or oxidized to form unreactive derivatives. Equally important, such sheets have the great disadvantage that they remain heat-sensitive even after imaging and must therefore be carefully stored away from heat or sunlight.

Another type of heat-sensitive copy sheet has been developed which consists of a colored foundation sheet having thereon an opaque blush coating which becomes transparent under the influence of heat to allow the colored foundation sheet to become visible. Such copy sheets are imaged in the same manner as the so-called reaction-type sheets discussed above. The principal disadvantages of these blush coated sheets are twofold. Most important is the fact that they are pressure-sensitive and thus subject to inadvertent marking during handling. Also, these copy sheets remain heat-sensitive and thus must be kept away from heat and sunlight.

It is thus an object of the present invention to provide for the production of clean, stable duplicate copies without the use of carbon paper or other pigmented transfer sheets.

It is another object of the present invention to prepare a heat-duplicating system which contains no color-forming dye components or chemical reactants.

It is still another object of the present invention to produce copies from an original sheet which are permanent in that they are resistant to the elfects of heat and pressure.

These and other objects are accomplished according to the present invention as more fully explained herein.

The invention consists in employing two layers, one of which is preferably present on a donor sheet and supplies a wax composition under the eliects of heat, and the other of which is preferably present on a receptor or copy sheet and becomes transparentized when heat-imaged with the wax composition of the donor sheet to allow the colored foundation of the receptor sheet to be visible in areas corresponding to the wax-imaged areas.

The receptor sheet consists of a foundation sheet with a colored surface having thereon a calcium carbonate layer which is rendered transparent when impregnated with wax.

The donor sheet carries a layer of heat-transferable wax composition. Under the effects of heat generated by the imaged areas of the original sheet, the donor layer melts or fuses and penetrates the calcium carbonate layer of the copy sheet to render it transparent in the preselected areas.

When the donor and receptor sheets are superposed together with an imaged original sheet so that the wax layer of the donor sheet is in contact with the waxtransparentizable layer of the receptor sheet, and the original sheet is against the donor sheet with its images facing the radiation source, and the superimposed sheets are subjected to infrared radiation, the images on the original sheet absorb the radiation and convert it to heat. This heat penetrates the donor sheet and melts the wax composition so that it is reduced to a fluid consistency. As such, the wax composition penetrates the calcium carbonate layer on the copy sheet and renders it transparent to allow the colored foundation sheet to become visible in areas corresponding to the imaged areas of the original sheet. Thus an exact copy is produced which cannot be inadvertently destroyed by heat or imaging pressure.

The essence of the present invention consists in the combination of a wax composition don-or sheet and a calcium carbonate copy sheet and their ideal suitability for the preparation of durable copies of an original in the thermo gr-aphic process.

Other features and advantages will hereinafter appear.

In the drawing:

FIGURE 1 is a diagrammatic fragmentary cross-section, to an enlarged scale, of the sheets of the present invention, together with an original sheet and under the influence of infrared radiation.

FIG. 2 is a diagrammatic fragmentary cross-section, to an enlarged scale, of the donor sheet and the imaged receptor sheet from FIG. 1 after removal from the radiation source and separation of the sheets.

FIG. 3 is a diagrammatic fragmentary cross-section, to an enlarged scale, of a copy sheet containing both the wax donor layer and the opaque calcium carbonate layer.

FIG. 4 is a diagrammatic view, to an enlarged scale, of a handy combination of a donor sheet and a copy sheet according to the present invention, releasably attached along one edge.

The present donor sheets consist of a suitable foundation sheet 10, such as paper or plastic film, carrying a heat-transferable wax-supplying layer 11. The layer 11 preferably consists solely of solid wax or a mixture of solid waxes. Such donor layer, in order to render the receptor layer transparent, must be melted and rendered fluid so that it can impregnate the calcium carbonate layer. Although layer 11 may be termed pressure-transferable, it has been found that a transfer of the solid wax composition under pressure will not transparentize the receptor layer since the unrnelted Wax composition does not impregnate the calcium carbonate'layer. This effect is important since the wax donor layer may be kept in surface contact with the calcium carbonate receptor layer for extended periods of time, and handled in contact as often as necessary without any chance of inadvertent imaging or staining of the receptor layer.

However, it should be understood that the present invention contemplates the method of thermographically imaging calcium carbonate receptor sheets regardless of the nature of the wax composition of the donor sheet. For instance, it has been found that some waxes have high melting points Which may be lowered through the addition of conventional plasticizers. The use of minor amounts of semi-solid or fatty materials such as lanolin, petrolatum and hydrogenated vegetable oils serves this purpose. Likewise the use of minor amounts of mineral, vegetable and animal oils will lower the melting point of wax compositions. Thus, although'it is known that such additives have impregnating powers of their own and that a donor layer containing these additives will transparentize the receptor layer under the effects of imaging pressure, nevertheless the present duplicating method contemplates the use of minor amounts of these additives.

No particular criticality exists 'in the selection of the waxes employed in the donor coating aside from the fact that they must be solid at temperatures over about 100 F. and must have a melting point between about 140- F. and 220 F. Among the suitable waxes are the ani mal, vegetable and mineral waxes such as microcrystalline Be Square, carnauba, raw montan, parafiin, beeswax, Carbowax, ouricury, as well as mixtures of these and other waxes. In general, it is preferred that the donor layer have a melting point of about l40l60 F. in which case a single wax such as microcrystalline Be Square wax may be used. When using a high melting wax such as carnauba, it is preferred to use it in admixture with a lower melting wax such as beeswax or paraffin wax.

The donor sheets are prepared by coating a suitable foundation sheet such as paper or plastic film with a thin layer of the wax composition, preferably by thehotmelt method.

The receptor sheets used in the present duplicating process comprise a foundation sheet, having at least one surface colored with a color which sharply contrasts with white, and having on the colored surface an opaque coating comprising finely divided calcium carbonate in a suitable binder. V

For instance, a suitable colored foundation sheet such as paper or plastic film is coated with a dispersion of calcium carbonate and sodium alginate, carboxymethyl cellulose, gelatin, gum arabic or the like, to form a white opaque layer 21. The preparation of such copy sheets is known to the art as shown for instance by U.S. Patent No. 2,854,350. This patent employs pressure-imaging donor sheets containing oil or petroleum jelly whereas the preferred donor sheets of the presentlinvention contain only wax and do not image the receptor sheet under pressure.

Prior to use, the receptor sheet has a white appearance since the opaque white layer hides the color of the underlying foundation sheet. However, when impregnated with the melted Wax composition according to the present process, the white opaque layer becomes permanently transparent in the treated areas, allowing the color of the underlying foundation sheet to become visible and form a permanent copy.

Where desired, the wax donor and the calcium carbonate layer may be present on the same copy sheet a exemplified by FIG. 3 of the drawing. In this embodiment, the wax layer is preferably applied as the underlayer. The calcium carbonate layer is applied thereover and, under the effects of heat, the wax flows into and transparentizes the opaque calcium carbonate layer and allows the colored underlayer to be visible in the imaged areas. It is important in this embodiment that the donor layer consist of wax or a mixture of Waxes so that itwill not image or stain the receptor layer by contact alone as is the case where oil or petroleum jelly is present in the donor layer.

Referring to the drawings:

The automatic production of copies is demonstrated by FiGS. l and 2 where an imaged original sheet 31 having images 31 which it is desired to copy, a donor sheet having foundation 10 and donor layer 11 and a receptor sheet having foundation 20 and receptor layer 21 are placed in intimate contact and subjected to infrared radiation for from two to twenty seconds to generate a temperature in the range of about 450 F. in the imaged areas. This may be accomplished through the use of a flat bed thermographic apparatus in which case the radiation is turned on for a few seconds, or through the use of a T hermo-Fax machine in which case the sheets are passed through at a moderate speed. The images 31 on the original sheet 30' absorb the radiation and convert it to heat. This heat then penetrates the donor sheet wherein the wax composition of the donor layer is reduced to a Howable condition and penetrates into the copy sheet to render receptor layer 21 transparent in areas corresponding to the imaged areas of the original. This allows the color of foundation 20 to become visible in the transparentized areas 22 to form a true copy.

In the situationwhere unitary self-imaging copy sheets are desirable, then the wax donor layer may be present on the copy sheet together with the calcium carbonate layer as shown by FIG. 3. To insure uniform stability and to protect against unintended imaging, the donor layer must contain only solid wax to the exclusion of any oil or semi-solid materials such as lanolin, petrolatum or hydrogenated vegetable oils which tend to image the receptor layer on contact.

FIG. 4 shows a handy duplicating pack comprising a donor sheet having foundation 10 and donor layer 11 together with copy sheet having foundation 20 and receptor layer 21, removably attached along one edge, such as by means of transverse severing lines 15 or the like.

It should be understood that the embodiments shown by the drawing are not to be interpreted as limitative. For instance, where desired for the production of many copies at one time, sheets may be employed which carry a calcium carbonate layer on the upper surface and a Wax releasing layer on the under surface. A number of such sheets may be superposed and heat-imaged at one time.

Variations and modifications may be made within the scope of the claims and portions of the improvements may be used without others.

I claim:

1. A system for preparing duplicate copies of an imaged original sheet through the use of infrared radiation, which comprises a donor sheet having a foundation bearing a color-free heat-meltable layer consisting of a Wax composition having a melting point of from 140 F. to 220 F., and a copy sheet having a colored foundation bearing. an opaque coating which is non-heat-transparentizable but which is capable of becoming transparent when impregnated with melted wax, the layer on the donor sheet not being capable of rendering the opaque coating of the copy sheet transparent under the effects of imaging pressure alone. I

2. A system for preparing duplicate copies of an imaged original sheet through the use of infrared radiation, which comprises a donor sheet having a foundation bearing a color-free heat-meltable layer consisting of a wax composition having a melting point of from 140 F. to 220 F., and a copy sheet having a colored foundation bearing an opaque coating comprising finely divided calcium carbonate in a form which is non-heat-transparentizable but which is adapted to become transparent when impregnated with melted wax, the layer on the donor sheet not being capable of rendering the opaque coating of the copy sheet transparent under the eifects of imaging pressure alone.

3. A system according to claim 2 in which the wax composition on the donor sheet consists solely of wax.

4. A system according to claim 2 in which the wax composition on the donor sheet contains a minor amount of mineral oil.

5. A system according to claim 2 in which the wax composition on the donor sheet contains a minor amount of at least one material selected from the group consisting of lanolin, petrolatum and hydrogenated vegetable oil.

6. A copy sheet designed for the production of a duplicate copy of an imaged original sheet through the use of infrared radiation, which comprises a colored foundation bearing two superposed layers, a first color-free heatmeltable layer consisting of a Wax composition having a melting point of from 140 F. to 220 F., and a sec ond opaque layer comprising finely divided calcium carbonate in a form which is non-heat-transparentizable but which is adapted to become transparent when impregnated with melted wax, the wax layer not being capable of rendering the opaque coating transparent under the effects of imaging pressure alone.

References Cited in the file of this patent UNITED STATES PATENTS 2,740,896 Miller Apr. 3, 1956 2,808,777 Roshkind Oct. 8, 1957 2,854,350 Phillpotts Sept. 30, 1958 2,859,351 Clark et al. Nov. 4, 1958 2,880,110 Miller Mar. 31, 1959 2,910,377 Owen Oct. 27, 1959 2,939,009 Tien May 31, 1960 

1. A SYSTEM FOR PREPARING DUPLICAT COPIES OF AN IMAGED ORIGINAL SHEET THROUGH THE USE OF INFRARED RADIATION, WHICH COMPRISES A DONOR SHEET HAVING A FOUNDATION BEARING A BEARING A COLOR-FREE HEAT-MELTABLE LAYER CONSISTING OF A WAX COMPOSITION HAVING A MELTING POINT OF FROM 140*F. TO 22/*F., AND A COPY SHEET HAVING A COLORED FOUNDATION BEARING AN OPAQUE COATING WHICH IS NON-HEAT-TRANSPARENTIZABLE BUT WHICH IS CAPABLE OF BECOMING TRANSPARENT WHEN IMPREGNATED WITH MELTED WAX, THE LAYER ON THE DONOR SHEET NOT BEING CAPABLE OF RENDERING THE OPAQUE COATING OF THE COPY SHEET TRANSPARENT UNDER THE EFFECTS OF IMAGING PRESSURE ALONE. 